JP2010067489A - Hybrid film for solid polymer fuel cell, its manufacturing method, membrane-electrode assembly, and solid polymer fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polymer electrolyte membrane solving both problems of a fluorine-based and hydrocarbon-based one at the same time. <P>SOLUTION: Hydrocarbon-based polymer electrolyte membrane solution is coated on the surface of a fluorine-based polymer electrolyte film at a masking rate of 50 to 80% and is dried to obtain a hybrid membrane for a solid polymer fuel cell with a hydrocarbon-based polymer electrolyte coated on the surface of the fluorine-based polymer electrolyte membrane at a coating rate of 50 to 80%. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a hybrid membrane for a polymer electrolyte fuel cell, a production method thereof, a membrane-electrode assembly used for a polymer electrolyte fuel cell, and a polymer electrolyte fuel cell having the same.

  The solid polymer electrolyte has a property of binding firmly to a specific ion or selectively transmitting a cation or an anion. In particular, a fluorine-based electrolyte membrane represented by a perfluorosulfonic acid membrane is used as a fuel cell ion exchange membrane used under severe conditions because of its very high chemical stability.

  However, while the fluorine-based electrolyte membrane is excellent in electric characteristics and chemical stability, the hydrogen gas permeability is inferior to the hydrocarbon-based electrolyte membrane. In particular, in order to improve battery performance, when thinning or low EW is implemented, hydrogen gas permeability increases, hydrogen fuel consumption increases, hydrogen to the oxidizer electrode or oxygen crossover to the fuel electrode Therefore, there is a concern about the decomposition of the electrolyte due to the generation of radical species that chemically degrade the electrolyte.

  In contrast, hydrocarbon membranes have high heat resistance, high oxidation resistance, high strength, and good proton conduction at room temperature, but the rigidity, hardness, etc. due to their molecular structure It is also a brittle material that comes from, and it is difficult to handle electrodes when assembling electrodes or assembling cells compared to fluorine-based electrolyte membranes.

  In order to achieve both proton conductivity / fuel gas permeability and handling properties, a hybrid material in which a porous base material is filled with an electrolyte having proton conductivity in its pores is disclosed in Patent Document 1 below. . Since an average pore diameter of 0.05 to 1 μm is obtained by filling the electrolyte in a very fine straight tube while reducing the pressure, a pressure reducing device or the like is required.

  In addition, as a method for producing a through hole, the method disclosed in Patent Document 2 below uses heat of a carbon dioxide laser, an excimer laser, or the like, and the center interval between the through holes is relatively large, about 50 μm to 100 μm. Therefore, the aperture ratio is about 10%, and a large proton conductivity cannot be obtained.

  Therefore, there is a demand for a method for maintaining the proton conductivity of the fluorine-based electrolyte membrane and reducing hydrogen gas permeation.

  Furthermore, the following patent document 3, the following patent document 4, and the following patent document 5 disclose an electrolyte membrane composed of a fluorine-based electrolyte membrane and a hydrocarbon-based electrolyte membrane, and a method for producing an electrolyte membrane electrode assembly. In contrast to hydrocarbon-based electrolyte membranes, fluorine-based electrolytes are used for the electrodes, and electrodes are prepared on the diffusion layer side, pastes are applied directly to the electrode membranes, and hydrocarbons are not disclosed. This indicates the poor bonding of dissimilar materials such as electrolytes and fluorine electrolytes.

  As a hydrocarbon electrolyte membrane, for example, in Patent Document 6 below, a main chain made by copolymerization of a fluorocarbon vinyl monomer and a hydrocarbon vinyl monomer, and a hydrocarbon side chain having a sulfonic acid group A sulfonic acid type polystyrene-graft-ethylene-tetrafluoroethylene copolymer (ETFE) membrane composed of: In addition, by introducing a crosslink into a sulfonic acid type polystyrene graft resin membrane similar to the sulfonic acid type polystyrene-graft-ETFE membrane described above, desorption of low molecular weight components during oxidative degradation is suppressed, and an electrolyte for a fuel cell Attempts have been made to improve the durability of the membrane.

  Further, in Patent Documents 7 and 8 below, α, β, β-trifluorostyrene is graft-polymerized on a film made by copolymerization of a fluorine-based vinyl monomer and a hydrocarbon-based vinyl monomer, and a sulfonic acid group is added thereto. A sulfonic acid type poly (trifluorostyrene) -graft-ETFE membrane has been proposed in which a solid polymer electrolyte membrane is introduced. This is based on the recognition that the chemical stability of the polystyrene side chain introduced with the sulfonic acid group is not sufficient, instead of styrene, α, β, β-trifluorostyrene obtained by fluorinating styrene. Is used.

  In addition, as the hydrocarbon-based ion exchange membrane, sulfonated polyether ether ketone (such as Patent Document 9 below), sulfonated polyether sulfone (such as Patent Document 10 below), sulfonated polysulfone (such as Patent Document 11 below), Sulfonated heat-resistant aromatic polymers such as sulfonated polyphenylene sulfide (such as Patent Document 12 below) and sulfonated polyimide (such as Patent Document 13 below), and SEBS (styrene- (ethylene-butylene) -styrene). Proton conductive membranes (such as Patent Document 15 below) composed of a sulfonated material (such as Patent Document 14 below) and a composite material of a proton conductivity imparting agent and an organic polymer compound have also been proposed.

JP 2005-158293 A JP 2005-108661 A JP 2005-276602 A JP 2006-73235 A Japanese Patent Laid-Open No. 2005-135681 JP-A-9-102322 US Pat. No. 4,012,303 US Pat. No. 4,605,685 JP-A-6-93114 Japanese Patent Laid-Open No. 10-45913 JP-A-9-245818 Japanese National Patent Publication No. 11-510198 JP 2000-510511 A Japanese National Patent Publication No. 10-503788 JP 2000-90946 A

  An object of the present invention is to provide a polymer electrolyte membrane that simultaneously solves both the problems of a fluorine-based polymer electrolyte membrane and a hydrocarbon-based polymer electrolyte membrane.

  The inventor of the present invention has the advantages of both hydrocarbon-based polymer electrolyte membranes and fluorine-based polymer electrolyte membranes. Hydrocarbon-based polymer electrolyte membranes have excellent gas barrier properties. Focusing on the fact that it is excellent in stability, it has been found that by combining the two, an excellent electrolyte membrane that solves the above-mentioned problems at the same time can be obtained, and the present invention has been achieved. That is, in the present invention, an electrolyte containing a hydrocarbon having a low hydrogen gas permeability (having proton transportability) is formed on the surface of the fluorine-based electrolyte, so that the fluorine-based electrolyte is maintained while maintaining proton conduction from the catalyst layer. Provided is a composite electrolyte membrane electrode assembly in which the gas permeation area of the membrane is reduced and furthermore, the electrolyte membrane and the electrode are firmly joined by a hot-pressure transfer method.

  First, the present invention is an invention of a hybrid membrane for a polymer electrolyte fuel cell, in which a hydrocarbon polymer electrolyte is coated on a surface of a fluorine polymer electrolyte membrane at a coverage of 50 to 80%. It is a hybrid membrane for polymer fuel cells.

  Second, the present invention is an invention of a method for producing a hybrid membrane for a polymer electrolyte fuel cell, wherein the surface of the fluorine-based polymer electrolyte membrane is masked at a coverage of 50 to 80%, A polymer electrolyte membrane solution is applied and dried.

  Third, the present invention is an invention of a membrane-electrode assembly (MEA) for a polymer electrolyte fuel cell comprising a pair of electrode catalyst layers and a polymer electrolyte membrane sandwiched between the electrode catalyst layers, The polymer electrolyte membrane is a hybrid membrane for a polymer electrolyte fuel cell in which a hydrocarbon polymer electrolyte is coated on a surface of a fluorine polymer electrolyte membrane at a coverage of 50 to 80%. .

  4thly, this invention is a polymer electrolyte fuel cell which has the said membrane-electrode assembly.

  In the present invention, an electrolyte containing a hydrocarbon having a low hydrogen gas permeability (having proton transport ability) is formed on the surface of the fluorine-based electrolyte, so that proton conduction from the catalyst layer is maintained while maintaining the proton conduction. It is possible to obtain a composite electrolyte membrane electrode assembly in which the gas permeation area is reduced and furthermore, the electrolyte membrane and the electrode are firmly joined by a hot-pressure transfer method.

  FIG. 1 shows a schematic cross-sectional view of a fluorine-based electrolyte membrane obtained by molding the hydrocarbon-based electrolyte of the present invention. A hydrocarbon-based electrolyte (low hydrogen gas permeation) partially covers the fluorine-based electrolyte membrane.

Conventional fluorine-based electrolyte membranes are as follows: 1) Hydrogen gas permeability (80 ° C., 50% RH) is about several hundred thousand (cc / m ² · 24 hr · atm) 2) Proton conductivity (S / cm @ 25 ° C.) The hydrous / fluorine electrolyte membrane of the present invention is 1) the hydrogen gas permeability (80 ° C., 50% RH) is tens of thousands (cc / m ² · 24 hr).・ Atm) degree, 2) Proton conductivity (S / cm @ 25 ° C. water) is about 0.07.

  In the present invention, the hydrocarbon-based polymer electrolyte means one having a C—H bond in any of the molecular chains and capable of introducing an ionic group. The ionic group means a functional group having proton conductivity such as a sulfonic acid group or a carboxylic acid group.

  Specific examples of the hydrocarbon polymer electrolyte include polyethersulfone resin, polyetheretherketone resin, linear phenol-formaldehyde resin, cross-linked phenol-formaldehyde resin, linear polystyrene resin, cross-linked polystyrene resin, Chain-type poly (trifluorostyrene) resin, cross-linked (trifluorostyrene) resin, poly (2,3-diphenyl-1,4-phenylene oxide) resin, poly (allyl ether ketone) resin, poly (arylene ether sulfone) ) Resin, poly (phenylquinosanline) resin, poly (benzylsilane) resin, polystyrene-graft-ethylenetetrafluoroethylene resin, polystyrene-graft-polyvinylidene fluoride resin, polystyrene-graft-tetrafluoroethylene resin, etc. And the like to.

Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples.
The reaction between the sulfonating agent and the polyimide amide resin proceeded as shown in the following reaction formula to obtain a hydrocarbon-based sulfonated resin.

  The resin material was used after being dried at 110 ° C. under reduced pressure for 5 hours. 5 times of sulfuric acid was added to 1 g of resin, and a sulfonating agent was further added to 1.0 times with respect to the resin, and the mixture was stirred for 1 day and night (24 hours) at room temperature for sulfonation.

  The obtained viscous liquid was dropped into about 10 times the amount of water while stirring, and washing and filtration were repeated until the pH of the water reached 7 with pH test paper (three times). After filtration, the obtained solid was dried in a vacuum dryer at 80 ° C. for 5 hours to obtain a sulfonated resin.

To measure the ion exchange equivalent weight, a sulfonated polymer to be measured was precisely weighed (a (gram)) in a glass container capable of being sealed, and an excessive amount of calcium chloride aqueous solution was added thereto and stirred overnight. Hydrogen chloride generated in the system was titrated (b (ml)) with 0.05N sodium hydroxide aqueous solution (titer f) using phenolphthalein as an indicator. From the above measured values, the ion exchange equivalent weight (g / mol) was determined by the following formula (1), and further converted to the ion exchange capacity (meq / g) using the following formula (2).
(Ion exchange equivalent weight [g / mo1]) = (1000 / a) / (0.05 × b × f) (Formula 1)
(Ion exchange capacity [meq / g]) = 1 / (ion exchange equivalent weight / 1000) (Equation 2)
By adding the same amount of chlorosulfuric acid to the polyamideimide resin, the ion exchange capacity was 0.9 [meq / g] equivalent to Nafion.

  The obtained hydrocarbon-based sulfonic acid resin was dissolved in a water / ethanol = 50/50 (volume ratio) solvent so as to be 5 wt% to obtain a hydrocarbon-based sulfonic acid resin solution.

  Nafion 112 (50 μm) Four sides are fixed so as not to shrink, and masked with punching metal so that the membrane surface area is hidden by 50% (hydrocarbon electrolyte area = 50%), masked to hide by 20% (hydrocarbon) System electrolyte area = 80%) and non-masking (hydrocarbon electrolyte area = 100%) were prepared. From this, the hydrocarbon-based sulfonic acid resin solution was repeatedly applied by a normal spray method. After coating, it was dried for 10 minutes with an 80 ° C. hot air dryer. The thickness of the obtained film was 55 μm.

[Gas permeation test]
Based on the JISK7126 A method (differential pressure method), the volume of gas that permeates the unit area per unit time was measured with a unit partial pressure difference for hydrogen gas at a temperature of 80 ° C. and a relative humidity of 50%. Table 1 below shows the results of hydrogen gas permeability.

表１の結果から、炭化水素系電解質面積が高いほどガス透過度が低いことが分かる。

From the results in Table 1, it can be seen that the higher the hydrocarbon electrolyte area, the lower the gas permeability.

[Measurement of proton conductivity]
After immersing the sample in hot water at 80 ° C. for 1 hour, the impedance is measured in 25 ° C. water using an impedance analyzer 1260 manufactured by Solartron, the resistance value is read from the Cole-Roll plot, and the proton conductivity is calculated. did. Table 2 below shows the proton conductivity test results.

表２の結果から、炭化水素系電解質面積とプロトン伝導度に相関性は見られない。

From the results in Table 2, there is no correlation between the hydrocarbon-based electrolyte area and the proton conductivity.

[Peel strength test results]
50 g of water, 50 g of ethanol, and 26 g of Nafion solution (DE2020CS, 21 wt% solution, manufactured by DuPont) with respect to 10 g of catalyst in which 45 wt% of platinum particles are supported on carbon black (Ketjen EC (manufactured by Ketjen Black International)) The stirred solution was irradiated with a sound wave for about 1 minute with a homogenizer, and cooled for 5 minutes because of heat generation, and a dispersion obtained by repeating this operation about 10 times was used as a catalyst ink for the air electrode.

This dispersion was applied onto a PTFE base material with a doctor blade type applicator so that the weight of platinum was 0.1 mg / cm ² and dried at 100 ° C. This was used as an electrode, and was transferred to the electrolyte membrane under conditions of 100 ° C., 3 MPa, and 4 minutes to prepare a composite electrolyte membrane electrode assembly.

The adhesiveness of the composite electrolyte membrane electrode assembly in which the electrolyte membrane and the electrode were joined by the hot-pressure transfer method was evaluated by a peel strength test in the 90 ° direction by peeling off the tape attached to the electrode surface.
Used adhesive tape: 3M-851A (manufactured by 3M)
Tape width: 15mm
Peel test speed: 10 mm / min Peel length: 50 mm
Table 3 below shows the results of the peel strength test.

  As shown in Table 3, when the hydrocarbon electrolyte area is 100%, the electrode is not bonded at all, but by setting the fluorine electrolyte membrane area to about 20%, the electrolyte membrane and the catalyst are sufficiently adhered to each other. Yes.

  By forming various electrolytes containing hydrocarbons with low hydrogen gas permeability on the surface of the fluorine electrolyte membrane, the hydrogen gas permeation area of the fluorine electrolyte membrane is reduced while maintaining proton conductivity from the catalyst layer, Provided is a fluorine-based electrolyte thin film that suppresses hydrogen gas permeation, and further can provide a composite electrolyte membrane electrode assembly in which an electrolyte membrane and an electrode are firmly bonded by a hot-pressure transfer method. It is effective for fuel cells.

  Furthermore, the hydrocarbon-based molding method with low hydrogen gas permeability is not limited to the spray method, and there are fine patterning molding methods such as a coating method, a screen printing method, an inkjet method, a dispenser method, a CVD method, and a sputtering method. Applicable. As the shape for reducing the hydrogen gas permeation area of the fluorine-based electrolyte membrane, any of geometric patterns such as dots, checkers, stripes, solid, coiled, and inclined shapes may be used.

  The material of the hydrocarbon electrolyte (having proton transporting ability) is not particularly limited, and polymers such as sulfonated polyphenylene sulfide, polybenzimidazole, polyetheretherketone, polyethersulfone, etc. Any copolymer can be applied. In addition, when preparing the polymer solution, N-methyl-pyrrolidone (NMP), dimethylformamide (DMF), dimethylol sulfoxide (DMSO) in addition to alcohol and water can be used if a solution in which the hydrocarbon electrolyte is dissolved is used. Etc. can be used together.

  By forming an electrolyte containing hydrocarbons with low hydrogen gas permeability on the surface of the fluorine electrolyte (having proton transport ability), the gas permeation area of the fluorine electrolyte membrane can be reduced while maintaining proton conduction from the catalyst layer. Further, it is possible to obtain a composite electrolyte membrane electrode assembly in which the electrolyte membrane and the electrode are firmly joined by a hot-pressure transfer method. This contributes to the spread of fuel cells.

The schematic cross section of the fluorine-type electrolyte membrane which shape | molded the hydrocarbon type electrolyte of this invention is shown.

Claims (4)

  A hybrid membrane for a polymer electrolyte fuel cell, in which a hydrocarbon polymer electrolyte is coated on a surface of a fluorine polymer electrolyte membrane at a coverage of 50 to 80%.   Production of a hybrid membrane for a polymer electrolyte fuel cell, characterized by masking the surface of a fluorine-based polymer electrolyte membrane at a coverage of 50 to 80%, and applying and drying a hydrocarbon-based polymer electrolyte membrane solution Method.   A membrane-electrode assembly (MEA) for a polymer electrolyte fuel cell comprising a pair of electrode catalyst layers and a polymer electrolyte membrane sandwiched between the electrode catalyst layers, the polymer electrolyte membrane comprising A membrane electrode for a solid polymer fuel cell, characterized in that it is a hybrid membrane for a polymer electrolyte fuel cell in which a hydrocarbon polymer electrolyte is coated at a coverage of 50 to 80% on the surface of the molecular electrolyte membrane Joined body.   A polymer electrolyte fuel cell comprising the membrane-electrode assembly according to claim 3.

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